The present invention relates to a bifurcated aortic prosthesis.
This prosthesis is intended to be implanted in the abdominal aorta of a human body to treat an aneurysm of the aortic bifurcation, that is to say an aneurysm located on the abdominal aorta between the point where the renal arteries branch off and the fork of the iliac arteries, generally close to this fork.
Many examples of such prostheses are known. By way of illustration, mention is made of the documents WO-97/40779, WO-95/21592, EP-0 880 948 and EP-0 461 791.
Document WO-95/21592 in particular discloses a bifurcated aortic prosthesis comprising:
a structure which comprises a main trunk which divides into two branches of equal lengths, and which is produced in such a way as to allow said prosthesis to adopt one of two positions: a folded and compact position to allow the prosthesis to be implanted in said aorta and a position in which it is implanted and deployed in the aorta to create a substitute passage in the region of said aneurysm; and
at least one impervious envelope at least partially enveloping said structure.
This prosthesis is small in size and is arranged near the renal arteries in such a way that it covers only a small part of the aneurysm. Two legs which just penetrate the iliac arteries are connected respectively to the said branches of the prosthesis. These legs thus cover the remainder of the aneurysm.
This embodiment has the drawback that the swirling flow of blood brought about by the aortic bifurcation (that is to say the fork at the iliac arteries) and which is generally responsible for the aneurysm moves upstream toward the renal arteries, something which is, of course, detrimental in the medium term and likely to cause a further aneurysm, in the vicinity of said renal arteries.
Furthermore, the structure of this prosthesis is such that it requires a significant amount of force to be generated in order to bring said prosthesis, when implanting it, from the folded position into the deployed position. This known document teaches the use of an inflatable balloon for generating such a force.
However, such use is difficult to perform and is also difficult to control. Furthermore, the inflating of the balloon completely cuts off the blood circulation, which makes it necessary to provide specific means or procedures for remedying the effects of a temporary interruption of the blood circulation.
Document EP-0 461 791 proposes, as an alternative to this implementation, a prosthesis which comprises a shape memory structure, which allows the structure to return automatically to the initial configuration, particularly the deployed configuration, without the use of specific means to achieve this.
The prosthesis described in that known document also differs from the one disclosed in document WO-95/21592 in that it has a far larger overall size, that is to say that both the trunk and the branches are larger, which means that the branches enter the iliac arteries over a relatively long distance. Furthermore, in a particular embodiment, the envelope completely covers said branches and partially covers said trunk. The envelope, which therefore penetrates the iliac arteries to a great extent, terminates at the other end well short of the renal arteries.
This known prosthesis has, as its major drawback, the fact that it is particularly tricky to fit and that this fitting requires a lengthy and complex procedure. This is because, in this case, the prosthesis is first of all brought from a femoral artery via an iliac artery into the aorta at the region of the aortic bifurcation and therefore the region of the aneurysm. For this purpose, the two branches of the prosthesis are continuous and introduced into one and the same delivery device. After the latter has been withdrawn, the two branches are located in one and the same iliac artery and one of said branches therefore has to be extracted from this iliac artery and led across into the other iliac artery.
This prosthesis is therefore particularly tricky and lengthy to fit.
The object of the present invention is to overcome these drawbacks. The invention relates to a bifurcated aortic prosthesis intended to be implanted in the aorta of a human body to treat an aneurysm of the aortic bifurcation, which prosthesis can be implanted simply and quickly, which allows effective treatment of the aneurysm and in addition prevents the aforementioned swirling flow of blood from moving back upstream toward the renal arteries.
To this end, said prosthesis, of the known type described, in particular, in document EP-0 461 791, and comprising:
a structure which comprises a main trunk which divides into two branches of equal lengths, which is of the shape memory type and which is produced in such a way as to allow said prosthesis to adopt one of two positions: a folded and compact position to allow the prosthesis to be implanted in said aorta and a position in which it is implanted and deployed in the aorta to create a substitute passage in the region of said aneurysm; and
at least one impervious envelope completely enveloping said branches and at least partially enveloping said trunk, is noteworthy, according to the invention, in that said envelope has a length such that, in said implanted position, it approximately covers that part of the aorta which lies between the renal arteries and the iliac arteries and in that the length of said branches is between xc2xc and ⅖ and is preferably close to ⅓ of the length of said envelope.
Thus, by virtue of the invention:
as the branches of the structure which are completely covered by the envelope do not enter the iliac arteries, the prosthesis is simpler and easier to fit, particularly by comparison with the aforementioned solution recommended by document EP-0 461 791. Furthermore, the length of said branches, although short, is long enough to allow a good grip and therefore, in particular, to allow additional legs to be assembled easily with the free ends of said branches. The fitting of the prosthesis is, of course, made easier by the use of a structure with shape memory;
since the entire region between the iliac arteries and the renal arteries is covered by the envelope, the entire aneurysm is treated (by the substitute passage created by the prosthesis). Of course, said envelope is made of a biocompatible material which, while being impervious to the flow of blood, remains permeable to cellular exchanges; and
since that part of the trunk which is covered by the envelope is very long (between ⅗ and xc2xe of the distance between the iliac aortas and the renal arteries), the swirling flow of blood caused by the aortic bifurcation is calmed at least greatly, if not completely, in this covered part and does not therefore travel back upstream toward the renal arteries.
According to the invention, the diameter of said branches is approximately equal to half the diameter of said main trunk. In consequence, the diameter of the branches is greater than in the aforementioned known prostheses, and this makes it possible to improve the flow of blood at the point where the branches connect to the trunk of the prosthesis.
Advantageously, at least one of said branches is flared at its free end, which makes it easier to attach an additional leg implanted in one of the iliac arteries.
Furthermore, advantageously, at the free end of at least one of said branches said envelope has a turned-back region, which allows it to seal with the additional leg assembled to said branch.
What is more, to fix the envelope to the structure in a robust and durable way, said envelope is sewn at least at its opposite end to the free end of the branches.
Furthermore, advantageously, the prosthesis according to the invention comprises at least one radio-opaque element, which allows the prosthesis to be readily detected and precisely pinpointed in the human body by radiography while it is being implanted and/or after it has been implanted. The radio-opaque element or elements used, for example known elements attached in a specific way, or preferably the linking means described hereinbelow, may be provided at various points on the structure. Advantageously, the prosthesis according to the present invention comprises:
at least one radio-opaque element arranged at the free end of at least one of said branches; and/or
at least two radio-opaque elements arranged on said structure in such a way as, in the implanted position, to delimit the branch connection of at least one of the renal arteries; and/or
a number of radio-opaque elements arranged in a V-shape and connecting the fork between the two branches, on the two sides of the trunk respectively, to the opposite end of the envelope to the branches.
In one preferred embodiment, said structure is at least partially produced in the form of a mesh and has at least one corrugated filament forming approximately annular units linked together. At least some of the corrugations of said corrugated filament of two adjacent units respectively are linked to one another by linking means. At least some of said linking means comprise links which are made as a rigid piece and provided with at least two loops joined together; and, in the case of each of said links, each of the two loops of said link entraps, with some clearance, a respective one of the two corrugations that are to be linked.
In the context of the present invention, some of the links may be radio-opaque and used as radio-opaque elements for allowing the detection of the prosthesis.